As agricultural policies continue to evolve away from traditional modes of support towards policies based upon or primarily influencing the market for land, it has become necessary to reconsider the way such policies are reflected in models. We demonstrate how the structure of land supply is constructed in the Policy Evaluation Model (PEM), and illustrate some potential options for representing land or historical entitlement-based programs using this model. Despite some basic similarities, the different choices for policy representation lead to significantly different model results. No policy may be considered to be entirely non-distorting of production decisions.